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High removal performance of a magnetic FPA90-Cl anion resin for bromate and coexisting precursors: kinetics, thermodynamics, and equilibrium studies

Xu, Zhengming, Han, Dexia, Li, Yuan, Zhang, Pingling, You, Lijun, Zhao, Zhengang
Environmental science and pollution research international 2018 v.25 no.18 pp. 18001-18014
Fourier transform infrared spectroscopy, X-ray diffraction, adsorption, anions, bicarbonates, bromides, carbonates, coprecipitation, drinking water, endothermy, iron oxides, kinetics, magnetism, maximum contaminant level, models, nitrates, pH, phosphates, scanning electron microscopy, sodium chloride, sorption isotherms, sulfates, temperature, thermodynamics
In this study, the FPA90-Cl resin was magnetized with supported Fe₃O₄ particles using a chemical co-precipitation method and its removal performance of bromate and coexisting precursors was explored. The magnetized FPA90-Cl resin was structurally characterized by SEM, FT-IR, and XRD. The effects of the initial concentrations, temperature, and resin dosage on bromate and bromide ion removal in drinking water were investigated using batch experiments. The magnetized FPA90-Cl resin exhibited a high removal efficiency for bromate and bromide ions at three initial concentrations, and the residual bromate concentrations were under the maximum contaminant level (MCL) of 10 μg L⁻¹ after 80 min. The adsorption data of bromate and bromide ion could be well described by a pseudo-first-order kinetic model (R² ˃ 0.98). The bromate removal alone was further studied by varying the initial solution pH, temperature, and competitive anions. The results showed that the magnetized FPA90-Cl resin could be used over a wide pH range (4.0–9.0). The maximum sorption capacity of the magnetized FPA90-Cl resin for bromate reached 132.83 mg g⁻¹ at 298 K. The Freundlich and Redlich-Peterson isotherm models fit the bromate adsorption equilibrium better (R² ˃ 0.99) than the Langmuir isotherm model (R² ˃ 0.98). The thermodynamic analysis showed that the bromate adsorption process was endothermic. The negative ΔG and positive ΔS indicated that the process was spontaneous and that randomness increased after adsorption, respectively. The competition of coexisting anions with bromate was in the order of SO₄²⁻ > CO₃²⁻ > Cl⁻ > NO₃⁻ > HCO₃⁻ > PO₄³⁻. Additionally, the magnetized FPA90-Cl resin could maintain a high bromate and bromide ion adsorption capacity after five cycles of regeneration by a 0.1 M NaCl solution. Graphical abstract